**4. Hydroxyapatite and essential oils**

One of the essential problems that limits crop production is the low availability of phosphorous (P) in many agricultural regions. In order to increase the phosphorous content in the soil it is necessary to apply P fertilizers, because phosphorous is an essential element for plant growth. Besides classical fertilizers, nanotechnology can offer a solution to supply the micronutrients deficiencies for plants development. In this regard, it was suggested [86] the use of hydroxyapatite nanoparticles Ca10(PO4)6(OH)2, nano-HAp, as potential fertilizers. Tests on the potential use of nano-HAp (15 nm) on soybean (*Glycine max*) [87] conduced to the conclusion that plants which received the nano-fertilizer produced greater biomass yield and seed compared with the plants fertilized with conventional water-soluble phosphorous source. It was stated [88] that nano-HAp might enhance P fertilizer efficiency in acidic and strongly P absorbing soils through the better mobility of nano-HAp in the soil potentially reaching plant roots. The experiments showed that the application of conventional triple superphosphate and HAp treatment conduced to an significantly increased the plant dry matter yield compared to control depending on soil characteristics e.g. Greenwood soils. The application of conventional fertilizer conduced to significant increase in shoot uptake of phosphorous in all types of soils in the range (0.1–1.4 mg P plant<sup>−</sup><sup>1</sup> ), in peculiar the application of nano-HAp increased the plant uptake to a maximum value of 0.4 mg P plant<sup>−</sup><sup>1</sup> , indicating a contribution uptake in percentage (40–61)%. These results suggesting that nanoparticles could possibly have a benefit over water-soluble P conventional fertilizers in the very strongly absorbing soils since the opportunities for P fixation in the soil is minimized.

Among other important plants for the use in medicine are those conducted to the extraction of essential oils as basil and lavender. Essential oils are complex biostructures and contain a lot of chemical compounds from different classes as: terpenoids, ketones, aldehydes and esters with a composition depending on the plant's origin and quality, harvest time, climate, soil and extraction method. About 90% of the bioactive components of essential oils are monoterpenes and in the oxygenated form the bioactivity is enhanced. The medical use of essential oils is based on their properties such as antibacterial, antifungal and their characteristic to prevent the growth of different pathogens. The antibacterial activity of HAp samples and HAp samples coated with essential oil of basil and lavender was tested on methicillin\_resistant *Staphylococcus aureus* (MRSA), *Staphylococcus aureus* 0364 and Gram-negative bacteria *Escherichia coli* ATCC 25922 as presented in [89]. As observed in **Figure 1(a–c)** there exists a slow decrease in MRSA growth for HAp-B and HAp-L samples at different concentrations—**Figure 1(a)**.

The evolution in the cell growth of *S. aureus* is observed in **Figure 1(b)**, an evolution that indicates a decrease in the cell growth starting from the low level concentration of 0.01 mg mL<sup>−</sup><sup>1</sup> in the presence of the HAp-B sample. The HAp-L inhibited *E. coli* (**Figure 1c**) starting with the concentration of 0.02 mg mL<sup>−</sup><sup>1</sup> . Taking into account that MIC is the lowest concentration of the chemical that prevents visible growth of bacteria, the lowest concentration of HAp-L nanopowders at which the visible inhibition of MRSA bacterial growth was observed was 0.039 mg mL<sup>−</sup><sup>1</sup> , and for HAp-B was 0.625 mg mL<sup>−</sup><sup>1</sup> . In the same conditions for *S. aureus* we have for HAp-B MIC value of 0.313 mg mL<sup>−</sup><sup>1</sup> and for *E. coli* HAp-L

**65**

**Figure 1.**

*values.*

MIC value was 0.039 mg mL<sup>−</sup><sup>1</sup>

. The antimicrobial properties of materials based

on hydroxyapatite coated with essential oils can be explained for HAp-B samples on the major component of hydroxyapatite as the basil essential oil was poorly

*Graphic representation of absorbance values of the microbial culture obtained in the presence of the plant EO-coated HAp on different bacterial strains MRSA (a),* S. aureus *(b) and* E. coli *(c) quantified by A620 nm* 

*Mentha* species are one of the most used medical herbs due to their chemical constituents as menthol and menthone. Peppermint (*Mentha piperita*) essential oils are used as remedies in coughs, colds, mouth sinuses, pain relief and headaches, with properties related to antiviral activity against influenza, herpes and

adsorbed onto the surface of hydroxyapatite nanoparticles.

*Application of Nanotechnology Solutions in Plants Fertilization*

*DOI: http://dx.doi.org/10.5772/intechopen.91240*

*Application of Nanotechnology Solutions in Plants Fertilization DOI: http://dx.doi.org/10.5772/intechopen.91240*

*Urban Horticulture - Necessity of the Future*

**4. Hydroxyapatite and essential oils**

types of soils in the range (0.1–1.4 mg P plant<sup>−</sup><sup>1</sup>

in the soil is minimized.

concentration of 0.01 mg mL<sup>−</sup><sup>1</sup>

response and in particular the distinct stress response. This is the reason why the complex process of utilization nanoparticles in agriculture has to be monitored to a level that avoids further environmental contamination i.e. soil, water and air.

One of the essential problems that limits crop production is the low availability of phosphorous (P) in many agricultural regions. In order to increase the phosphorous content in the soil it is necessary to apply P fertilizers, because phosphorous is an essential element for plant growth. Besides classical fertilizers, nanotechnology can offer a solution to supply the micronutrients deficiencies for plants development. In this regard, it was suggested [86] the use of hydroxyapatite nanoparticles Ca10(PO4)6(OH)2, nano-HAp, as potential fertilizers. Tests on the potential use of nano-HAp (15 nm) on soybean (*Glycine max*) [87] conduced to the conclusion that plants which received the nano-fertilizer produced greater biomass yield and seed compared with the plants fertilized with conventional water-soluble phosphorous source. It was stated [88] that nano-HAp might enhance P fertilizer efficiency in acidic and strongly P absorbing soils through the better mobility of nano-HAp in the soil potentially reaching plant roots. The experiments showed that the application of conventional triple superphosphate and HAp treatment conduced to an significantly increased the plant dry matter yield compared to control depending on soil characteristics e.g. Greenwood soils. The application of conventional fertilizer conduced to significant increase in shoot uptake of phosphorous in all

nano-HAp increased the plant uptake to a maximum value of 0.4 mg P plant<sup>−</sup><sup>1</sup>

indicating a contribution uptake in percentage (40–61)%. These results suggesting that nanoparticles could possibly have a benefit over water-soluble P conventional fertilizers in the very strongly absorbing soils since the opportunities for P fixation

Among other important plants for the use in medicine are those conducted to the extraction of essential oils as basil and lavender. Essential oils are complex biostructures and contain a lot of chemical compounds from different classes as: terpenoids, ketones, aldehydes and esters with a composition depending on the plant's origin and quality, harvest time, climate, soil and extraction method. About 90% of the bioactive components of essential oils are monoterpenes and in the oxygenated form the bioactivity is enhanced. The medical use of essential oils is based on their properties such as antibacterial, antifungal and their characteristic to prevent the growth of different pathogens. The antibacterial activity of HAp samples and HAp samples coated with essential oil of basil and lavender was tested on methicillin\_resistant *Staphylococcus aureus* (MRSA), *Staphylococcus aureus* 0364 and Gram-negative bacteria *Escherichia coli* ATCC 25922 as presented in [89]. As observed in **Figure 1(a–c)** there exists a slow decrease in MRSA growth for HAp-B

The evolution in the cell growth of *S. aureus* is observed in **Figure 1(b)**, an evolution that indicates a decrease in the cell growth starting from the low level

inhibited *E. coli* (**Figure 1c**) starting with the concentration of 0.02 mg mL<sup>−</sup><sup>1</sup>

Taking into account that MIC is the lowest concentration of the chemical that prevents visible growth of bacteria, the lowest concentration of HAp-L nanopowders at which the visible inhibition of MRSA bacterial growth was observed was

in the presence of the HAp-B sample. The HAp-L

. In the same conditions for

and for *E. coli* HAp-L

and HAp-L samples at different concentrations—**Figure 1(a)**.

, and for HAp-B was 0.625 mg mL<sup>−</sup><sup>1</sup>

*S. aureus* we have for HAp-B MIC value of 0.313 mg mL<sup>−</sup><sup>1</sup>

), in peculiar the application of

,

.

**64**

0.039 mg mL<sup>−</sup><sup>1</sup>

#### **Figure 1.**

*Graphic representation of absorbance values of the microbial culture obtained in the presence of the plant EO-coated HAp on different bacterial strains MRSA (a),* S. aureus *(b) and* E. coli *(c) quantified by A620 nm values.*

MIC value was 0.039 mg mL<sup>−</sup><sup>1</sup> . The antimicrobial properties of materials based on hydroxyapatite coated with essential oils can be explained for HAp-B samples on the major component of hydroxyapatite as the basil essential oil was poorly adsorbed onto the surface of hydroxyapatite nanoparticles.

*Mentha* species are one of the most used medical herbs due to their chemical constituents as menthol and menthone. Peppermint (*Mentha piperita*) essential oils are used as remedies in coughs, colds, mouth sinuses, pain relief and headaches, with properties related to antiviral activity against influenza, herpes and

other viruses. The influence of peppermint essential oil (P-EO) on the surface of hydroxyapatite nanoparticles was studied [90] related to their morphological, physicochemical and antimicrobial properties. The results of the qualitative antimicrobial properties of P-EO and HAp-P are presented in **Table 1**.

Antimicrobial qualitative assay revealed that the peppermint had a significant inhibition effect on the microbial growth of the tested microorganisms, with the inhibition diameter ranging from 6 to 22 mm. The solvent DMSO did not affect the growth on solid media of any tested microbial strains. HAp had no inhibitory effect on the growth of the tested microorganisms and the most pronounced inhibition was observed in the case of *E. coli* tested strains in its two forms. The diameter of the inhibition growth area was 22 mm to 20 mm in the case of P-EO and a smaller inhibition zone of 8 mm for HAp-P. On *S. aureus* the inhibitory effect was related notably for P-EO and HAp-P with an inhibition zone in the range 7–8 mm. Essential oil extracted from peppermint contains active constituents that are responsible for eliminating bacterial pathogens, i.e. P-EO and HAp-P presented significant antibacterial activity with constituents acting on the cell membrane causing important morphological damage and destabilization of microbial membrane. Due to the worldwide emergence of *S. aureus* and *E. coli* strains which are resistant to conventional antibiotic therapy, there have been major concerns in public health area that conduced to the necessity of the developing of new antimicrobial compounds. Nano-sized powders of HAp doped with several metal ions that are known to possess antimicrobial properties as silver, zinc or cerium are used together with HAp in combination with essential oils. The effect of plants EOs and plants EOs-HAp combination regarding the antimicrobial activity is presented [91] in **Table 2** related to the diameter of inhibition zone-inhibition growth of tested bacterial strains.

The lavender EO inhibited the growth of all tested bacterial strains, as indicated the formation of inhibition zone ranged from 16 mm (*E. coli* ESBL 4493) to 24 mm (MRSA 1144). The HAp-L material was active against tested bacterial strains compared to HAp. The basil EO and HAp-B samples exhibited a lower inhibitory effect against the tested bacteria. On the other hand, HAp material had no effect on the growth of the selected bacteria.

The possibility of covering hydroxyapatite with different molecules, e.g. essential oils offer a solution to apply in food industry, in the idea that HAp is an essential component of human organism. In this regard, the potential use in medicine e.g. bone reconstruction could help the reducing of postoperative infections after different implants. In the case of hydroxyapatite nanotechnology have opened the gate to different applications in agriculture, food industry, medicine with the final target of improving human health and resistance to a continuous modification of pathogen agents.


**67**

**Acknowledgements**

*Application of Nanotechnology Solutions in Plants Fertilization*

As it was presented, in the last few decades, nanotechnology reveals its benefit usage in different activity fields and in particular in biotechnology and agriculture. Fertilizer compounds are essential for our quality of soil and water for the development of plants in order to increase the crops in order to cover what is needed to sustain the food necessities all over the world. Therefore there exist a necessity to decrease nutrient casualties in fertilization, and to amplify the plant product by the operation of novel uses with assistance of nanotechnology and nanomaterials. This type of fertilization delivers the nutrients on request, control the use of chemical fertilizers that regulate growth and development of plants and raise the activity of target vegetal organism. In this regard have been presented the effects of different nanomaterials and nanoparticles upon selected plants culture as wheat, maize, soybean, etc. taking into account their growth morphological parameters and the nanoparticles influence upon plant metabolism. The present and future use of nanoparticles as micronutrients is affected by different risks related to nanotoxicity of micronutrients, a problem to be solved by an appropriate and safe circuit of nanoparticles in soil, water, plants and at last in human organism. In this regard, it is important to quantify nanomaterials concentration in water, soil and air, where the concentration of relevant nanomaterials is essential to define exposure, a problem to be solved by the modeling of environmental concentrations. Due to the rapid development of manufactured nanomaterials it is important to evaluate their environmental and health impact, and it was stated to assure a safe circuit from micronutrients used for plants crop increasing to the beneficiaries of these plants, i.e. animals and humans. The present work is an approximately extensive presentation of the present status of the application of nanomaterials and nanoparticles in agriculture i.e. in plants fertilization with accent to the plants growth parameters,

*Antimicrobial activities of plant EOs, HAp-B and HAp-L against Gram-positive and Gram-negative bacteria.*

possible toxic risks and application to the antimicrobial activity.

The authors thank for financial support to Romanian Ministry of Research and

Innovation Contract No. 43PCCDI/2018 and Contract No. 23PCCDI/2018.

*DOI: http://dx.doi.org/10.5772/intechopen.91240*

**5. Conclusions**

**Table 2.**

#### **Table 1.**

*The diameters of inhibition growth zones (mm).*


**Table 2.** *Antimicrobial activities of plant EOs, HAp-B and HAp-L against Gram-positive and Gram-negative bacteria.*
